In certain applications, it is desirable to deposit flock or fiber material topically onto the surface of a substrate to form a coating. Alternatively, fibers are injected into the substrate to form a layer therein or a blend with one or more other materials forming the substrate. The fiber material employed can be synthetic or organic and vary in size from a few thousandths of an inch to one inch or longer. In some applications, an electrostatic charge is imparted to the fiber material so that it is attracted and adheres to a target object or surface held at ground or a different electrical potential. Alternatively, the fiber material is ejected onto a surface coated with an adhesive material so that the fibers adhere thereto.
Prior art systems for spraying fiber material onto a substrate or object generally comprise a hopper in which the fibers are loaded in bulk quantities, a chamber wherein fibers discharged from the hopper are entrained in a stream of air and a spray device communicating with the chamber for ejecting the air-entrained fiber material onto a substrate or other object. Systems of the type described above have a variety of mechanical elements for handling and transmitting the fibers which are designed to obtain a relatively uninterrupted and steady flow of fibers throughout the system so that a uniform pattern of fibers is discharged from the spray gun.
For example, hoppers in the fiber spray systems mentioned above are formed with an opening through which fibers are dispensed into an air entrainment chamber and such openings are often provided with a perforated grid or other closure mechanism to control the flow rate of fibers therethrough. Additionally, various devices have been provided for mechanically directing the particles through the opening in the hopper such as rotating paddles as shown in U.S. Pat. Nos. 4,560,307 to Deitesfeld; 3,347,469 to Ross et al; and, 3,551,178 to Chmelar; screw feeders as shown in U.S. Pat. Nos. 3,907,170 to Schedrin et al; and, 2,889,083 to Schwinhorst; and, rotating brushes such as disclosed in U.S. Pat. No. 4,311,113 to Jordan. Each of these mechanisms are carried within the interior of the hopper and function to push or force fiber material through an opening in the hopper and into a chamber for entrainment in a stream of air.
Regardless of the construction of the hopper and/or fiber feeding devices, it is desirable to not only provide for a uniform flow or discharge of fibers from the hopper, but to also permit adjustment of the feed rate of fibers therefrom. Additionally, fiber spray systems are preferably adapted to handle fibers of different size and/or density to accommodate different spraying applications. Each of the systems described in the patents listed above have one or more operating deficiencies which limits the capability of such systems to adapt to different types of applications and/or to certain kinds of fibers and not others.
Another important aspect of fiber spraying systems is to ensure that the air-entrained fibers are transmitted through the system and discharged from the spray gun without the fibers clumping or bunching together. In most systems, the fibers are discharged from the feed hopper into a chamber or tube connected to a pump which entrains the fibers in a stream of air and then forces the air-entrained fibers through a hose connected to a spray device located remotely from the pump. Although many systems are effective in entraining the fiber material in a stream of air, a relatively long flow path is often provided between the pump and the spray device along which the fibers can clog or bunch together. This can produce a pulsating or uneven discharge of fibers from the spray device which is unacceptable in many spraying applications.